WO2021129155A1 - Process for synthesizing composite piperazine-based heavy metal chelating agent tddp - Google Patents

Abstract

Disclosed is a process for synthesizing a composite piperazine-based heavy metal chelating agent TDDP, the process comprising the following reactions: a condensation reaction of ethylenediamine and glyoxal as raw materials in the presence of a catalyst to produce piperazine-fused piperazine; a reaction, with an organic base tetramethyl guanidine as a catalyst, of the piperazine-fused piperazine with carbon disulfide and sodium hydroxide to produce TDDP; and at the same time a reaction of ethylenediamine with carbon disulfide and sodium hydroxide to produce EDTC. Compared with the prior art, the beneficial effects of the present invention lie in that: during the preparation of TDDP from a solution, in which the piperazine-fused piperazine has been synthesized, under designed reaction conditions, excess ethylenediamine is reacted with carbon disulfide and sodium hydroxide to produce another heavy metal precipitating agent EDTC, so that a removing agent having both a cyclic structure and a linear structure with the function of removing heavy metal ions can be obtained from the prepared target product, the heavy metal chelating agent, without secondary combination, thereby expanding the field of use and making the effect of removing heavy metal ions particularly obvious.

Description

Synthesis process of a composite piperazine heavy metal chelating agent TDDP Technical field

The invention belongs to the technical field of environmental functional materials, and in particular relates to a synthesis process of a composite piperazine heavy metal chelating agent TDDP. The composite piperazine heavy metal chelating agent can be used for the removal of heavy metals in waste water and fly ash.

Background technique

In recent years, ethylenediamine, glyoxal, sodium hydroxide, carbon disulfide, etc. have been used as raw materials to synthesize N,N,N,N-4 (dithiocarboxyl) dioxopiperazine sodium salt (TDDP for short). The main component of the chelating agent has obvious advantages in the removal of heavy metal ions, the reduction of sludge, and the flocculation effect. This type of chelating agent can react with various heavy metal ions in the wastewater to stabilize the discharge up to the standard, and the heavy metals produced after treatment Chelated flocs have good stability and are not easy to cause secondary pollution; and in terms of application, TDDP can be directly put into use on the original chemical precipitation device without major changes to the wastewater treatment system, which is more convenient to use; its performance is stable, acid and acid resistance Alkali, the chelating agent is a high-steady-state macromolecular substance, applicable to a wide pH range, does not need to adjust the pH of the wastewater multiple times, and can save the cost of acid and alkali chemicals.

The existing research results of EDTC heavy metal chelating agents related to TDDP and the intermediate bis-piperazine, as well as the synthesis of ethylenediamine, mainly include:

Lu Ming et al. published a paper "1,4,6,9-tetranitro-1,4,6,9-tetraazabicyclo[4,4, 0] Decane synthesis process improvement" The mechanism and influencing factors of the reaction of ethylenediamine and glyoxal as raw materials to synthesize diopiperazine were studied, and the reaction yield was 77.5%.

In his master's thesis "Ionic Liquid Catalyzed Aldamine Condensation Reaction to Prepare Nitrogen Heterocyclic Compounds" (Nanjing University of Science and Technology, 2016), Zhou Zhilei proposed a study on the synthesis of dioxopiperazine catalyzed by ionic liquids, and the pilot production rate of dioxopiperazine was as high as 93 %, but no method for comprehensive utilization of excess ethylenediamine is proposed;

In his master's thesis "Synthesis and Application Research of Heavy Metal Collector TDDP" (Zhengzhou University, 2018), Feng Xiu proposed that ethylenediamine and glyoxal are used as raw materials to condense under alkaline conditions to form 2,3-di Hydroxypiperazine, then dihydroxypiperazine molecules are dehydrated to prepare diopiperazine, and then use diopiperazine and carbon disulfide to synthesize TDDP in ethanol-water mixed solvent, focusing on the main influencing factors of the second step of synthesis, By comparing the amount of reactants, the ratio of ethanol to water, the reaction temperature and time, the optimal synthesis conditions are initially obtained.

Chinese Invention Patent Publication No. CN101642612A proposes to use p-diazepine and aminoethyl p-diazepine products with similar structure to TDDP as a chelating agent for stabilizing heavy metals. Although it has a good removal effect, the amount is too large. (Sometimes even the amount reaches 10% of the weight of the material to be processed), the use cost is relatively high.

Based on the above disclosed technologies, the main problems existing in the existing synthesis process of diopiperazine and TDDP are:

(1) There are the following problems when synthesizing the intermediate raw material dioxopiperazine of TDDP:

①The ratio of ethylenediamine and glyoxal materials is unreasonable, resulting in low yield of dipiperazine;

②Improper selection of reaction temperature results in the formation of jelly (the jelly is initially analyzed as a polymer of glyoxal) during the reaction, making the reaction unable to proceed according to the designed direction;

③The endpoint of the reaction cannot be accurately determined, resulting in a low yield of dipiperazine;

(2) The following problems exist when using diopiperazine, carbon disulfide, and NaOH to synthesize TDDP:

①Long reaction time, more than 5 hours is required for the synthesis reaction alone;

②The ratio of raw materials is unreasonable, especially the excessive amount of carbon disulfide;

③The yield of product TDDP is low. Too many by-products of various structures in TDDP sometimes lead to poor removal of heavy metal ions, and disadvantages such as insufficient discharge concentration after wastewater treatment;

Summary of the invention

In the in-depth study of the existing TDDP synthesis process material ratio, reaction temperature control, reaction time, etc., it is found that the existing TDDP synthesis in China has no stepwise control of the reaction temperature, which leads to the failure of the reaction, the unreasonable ratio of raw materials, and the long reaction time. , Multiple side reactions and other defects, the technical problems to be solved by the present invention include:

1. Improve the yield of dioxopiperazine, an intermediate raw material for the synthesis of ethylenediamine and glyoxal;

2. Shorten the reaction time;

3. Reasonably determine the ratio of bis-piperazine, sodium hydroxide solution, and carbon disulfide, especially the excess ratio of carbon disulfide; in the prior art, due to process conditions and catalysts, the excess carbon disulfide generally exceeds 10% of the theoretical ratio. The purpose is Improve the yield of the final product TDDP, but it also brings more side reactions, resulting in high product cost and poor efficiency;

4. Improve the yield of finished products with TDDP as the target product;

5. Make full use of the excess ethylenediamine that is not involved in the reaction during the preparation of di-piperazine to synthesize another heavy metal treatment agent to improve the economic benefits of the product.

The technical method of the present invention is as follows:

The synthesis process of a composite piperazine heavy metal chelating agent TDDP includes the following reactions:

Using ethylenediamine and glyoxal as raw materials, condensation reaction occurs in the presence of a catalyst to produce dioxopiperazine;

Using the organic base tetramethylguanidine as a catalyst, dioxopiperazine reacts with carbon disulfide and sodium hydroxide to generate TDDP; at the same time, ethylenediamine reacts with carbon disulfide and sodium hydroxide to generate EDTC.

Among them, N,N,N,N-4 (dithiocarboxyl) dioxopiperazine sodium salt (TDDP) is generated in step 2. The reaction mechanism is a nucleophilic addition reaction, and the strong organic base tetramethylguanidine and Under the action of the strong inorganic base sodium hydroxide, the secondary amine of the heterocyclic compound dipiperazine reacts with the hydroxide ion to form a secondary amine anion. The secondary amine anion attacks the carbon atom on the carbon disulfide carbon sulfur group to form a carbanion intermediate, and then It interacts with positively charged sodium ions to obtain the target product.

Preferably, the synthesis process includes the following operation steps:

Step 1. Material preparation: After measuring the ethylenediamine, suck it into the first reaction kettle with a vacuum, add the catalyst, and turn on the stirring;

Prepare glyoxal into a glyoxal aqueous solution, and pump it into the glyoxal high tank;

Prepare NaOH solution and pump it into the NaOH intermediate tank;

Use compressed air to press carbon disulfide from the storage tank into the carbon disulfide intermediate tank (must ensure that the height of the carbon disulfide intermediate tank used as liquid sealing water is not less than 15mm), and press it into the carbon disulfide high tank twice (must ensure that the high tank is used as liquid The height of the sealing water is not less than 15mm).

Step 2. Synthesis of diopiperazine: Under the state of stirring and starting, pass the cooling liquid into the jacket of the first reactor, and wait until the temperature in the first reactor drops to -5～0℃, and then start to feed the first reactor. Add glyoxal aqueous solution dropwise to control the dropping rate to maintain the reaction temperature at 2～10℃;

After the dropwise addition of the glyoxal aqueous solution is completed, use compressed air to press the materials from the first reactor to the second reactor, and steam into the jacket of the second reactor, heat up to 47～52℃, and react for 30～50 minutes; , Open the steam valve, raise the temperature of the kettle to 55～67℃, continue the reaction for 30～50 minutes; reduce the temperature of the kettle to below 35℃, add a certain amount of water to the second reactor to adjust the concentration of di-piperazine Higher than 20%.

Step 3. Synthesis of TDDP as the main target product: press the product obtained in step 2 from the second reactor into the third reactor with compressed air, add the catalyst tetramethylguanidine and NaOH solution, and stir it fully; to the third reactor Cooling liquid is passed into the jacket, and after the temperature in the kettle drops to 0-5°C, carbon disulfide is added dropwise to the third reaction kettle from the high-position tank of carbon disulfide, and the reaction temperature in the kettle is controlled to be 20-32°C.

Step 4. Secondary reaction: Step 3 After the addition of carbon disulfide is completed, use compressed air to press the product obtained in Step 3 from the third reactor into the fourth reactor, and steam into the jacket of the fourth reactor to make the The temperature is increased to 45-60°C in 20-50 minutes, and the reaction is continued at this temperature for 40-70 minutes.

Step 5. After the reaction is over, add water to the reaction liquid of the fourth reactor, take samples and analyze, and after the test is qualified, pack and store.

Preferably, the catalyst in step 1 is tetrahydroquinoline;

Preferably, the molar ratio of glyoxal to ethylenediamine in step one is 1: (4.01-4.09);

Preferably, the molar ratio of the glyoxal to carbon disulfide is 1: (8.06-8.12);

Preferably, the molar ratio of the glyoxal to NaOH is 1: (8.8-10.4); wherein the glyoxal and NaOH are both calculated as 100%.

Preferably, the amount of the catalyst tetrahydroquinoline is 0.02-0.2% of the weight of glyoxal;

Preferably, the amount of the catalyst tetramethyl biguanide is 0.05-0.5% of the weight of glyoxal;

The synthesis process of a composite piperazine heavy metal chelating agent TDDP provided by the present invention has the following characteristics:

1. When preparing di-piperazine, according to the reaction mechanism of ethylenediamine and glyoxal and the characteristic of ethylenediamine excess, in addition to adopting a gradient temperature increase and determining the optimal temperature operation, basic organic compounds are added as a catalyst during synthesis. On the one hand, it significantly increases the conversion rate of glyoxal and at the same time increases the yield of di-piperazine. On the other hand, it reduces the amount of colloid that reduces the polymerization reaction and internal cyclization reaction of glyoxal and ethylenediamine. Etc., thereby improving the yield of di-piperazine;

2. The organic base tetramethylguanidine is used as a catalyst when synthesizing TDDP, which has a synergistic effect on the reaction with the inorganic strong base sodium hydroxide, which can speed up the reaction speed of dioxopiperazine, carbon disulfide and sodium hydroxide, and shorten the reaction time.

3. When synthesizing TDDP, the reaction temperature is controlled in stages. According to the reaction mechanism and reaction characteristics, low temperature is used for the primary reaction, and the temperature is increased for the secondary reaction, which reduces the loss of carbon disulfide gas and improves the conversion rate of dipiperazine;

4. Determine the reasonable ratio of raw materials and optimize the reaction conditions. The reasonable molar ratio of carbon disulfide to bis-piperazine is controlled, the excess carbon disulfide is small, and the reaction is more thorough; during the reaction process, due to the reasonable selection of process parameters, there will be no black spots (small elemental carbon particles) caused by the decomposition of carbon disulfide in the system. ) And yellowish particles (fine elemental sulfur particles), the appearance and internal quality of the finished product meet the index requirements.

5. When synthesizing diopiperazine, the goal is to obtain diopiperazine solution instead of solid diopiperazine; fully consider the use of ethylenediamine remaining in the diopiperazine solution, diopiperazine, Ethylenediamine reacts with sodium hydroxide and carbon disulfide to produce TDDP and EDTC. The product contains two kinds of chelating agents with nitrogen-containing cyclic compound TDDP and linear structure EDTC. The two compounds with different structures act synergistically when processing heavy metal ions, and the effect of removing heavy metal ions is significantly better than the current single chelating agent. .

6. The product synthesis process is simple, the reaction conditions are mild and easy to control, and the yield is high. The carbon disulfide discharged by the activated carbon fiber combined device is used to adsorb and recycle, and the exhaust gas discharged meets the national emission standard. No three wastes are discharged from the production device.

7. Product treatment of waste water containing heavy metal ions meets the discharge standards, and the treatment of incineration waste fly ash and various industrial fly ash meet the landfill standards.

Compared with the prior art, the beneficial effect of the present invention is: under the designed reaction conditions, the solution after the synthesis of diopiperazine while preparing TDDP, excess ethylenediamine reacts with carbon disulfide and sodium hydroxide to form another A kind of heavy metal precipitant EDTC, so that the prepared heavy metal chelating agent target product can be obtained without secondary compounding to obtain a remover that has both a ring structure and a linear structure to remove heavy metal ions, which expands the field of use and removes heavy metal ions. Especially obvious.

Detailed ways

It should be pointed out that the following detailed descriptions are all exemplary and are intended to provide further description of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

It should be noted that the terms used here are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and/or "including" are used in this specification, they indicate There are features, steps, operations, devices, components, and/or combinations thereof.

In the TDDP synthesis process, after studying the influence of the process operating conditions on the product yield and raw material conversion rate, the following are as follows:

1. The influence of reaction temperature

According to the principle of the condensation reaction between glyoxal and ethylenediamine, the reaction temperature control has the greatest impact on the conversion rate of glyoxal and the yield of dipiperazine. When 40% glyoxal is added dropwise, if the temperature is too low, ethylenediamine will hardly react with glyoxal; if the reaction is kept at a high temperature at the beginning of the reaction, the solution will quickly change from transparent to turbid, forming a gluey substance attached On the reaction vessel; if the reaction temperature is controlled at about 40°C, the reaction speed is very slow, and the conversion rate of glyoxal is still very low after a long time of reaction, and the time required to reach the end of the reaction is sometimes as long as tens of hours.

2. The influence of reaction time

The reaction time is closely related to the reaction temperature. In the study, it was found that: mixing glyoxal and ethylenediamine at a temperature lower than 40℃ for a long time without reaction, the reaction system is a uniform and transparent liquid; if glyoxal and ethylenediamine are mixed, the temperature rises to 70 immediately At about ℃, the reaction speed is very fast but will form a resinous by-product which will affect the yield of diopiperazine; this shows that: the condensation reaction of glyoxal and diamine firstly generates 2,3-dihydroxypiperazine at a low temperature stage, and then at a high temperature Phase dehydration with ethylenediamine to form a condensation product, if it is directly condensed at high temperature without the addition reaction of the low temperature stage, glyoxal will polymerize with ethylenediamine to form a chain polymer (colloid product) to make dioxin piperazine The yield is reduced.

3. The impact of catalysts

At present, the main catalysts for the synthesis of diopiperazine are ionic liquids, but the preparation of ionic liquids is cumbersome and the use conditions are harsh. There are currently no reports and literature on the use of tetrahydroquinoline as the catalyst. The variety and amount of catalyst used in amine-aldehyde condensation have a greater impact on the synthesis of diopiperazine. Ethylenediamine is dissolved in water to form a strong alkaline solution, while 40% glyoxal solution is acidic. The overall environment of the two reactions is relatively basic. Once an acidic catalyst is used, it may lead to the formation of ethylenediamine salt. Therefore, basic catalysts are used in actual research. Combining the characteristics of the reaction, it was determined to use tetrahydroquinoline as the catalyst after screening.

4. The solution after synthesizing diopiperazine is reacted with NaOH and carbon disulfide to prepare the target product. One is to generate TDDP, and the other is to generate linear chelating agent EDTC. The linear chelating agent EDTC itself is also a compound with a relatively simple structure. It is prepared by the reaction of ethylenediamine, carbon disulfide and sodium hydroxide. The product is produced at the same time when preparing TDDP. It is also a good heavy metal chelating agent. The products have good effects in removing heavy metal ions and have a synergistic effect. Catalyst selection, material ratio, reaction temperature and time have a greater impact on the yield of the final product and the capture effect of heavy metal chelating agents.

Example 1: Synthesis process of composite piperazine heavy metal chelating agent TDDP

1. Preparation of raw materials: After measuring 525 kg of ethylenediamine and sucking it into the first reactor with a vacuum, add 150 g of tetrahydroquinoline, turn on the stirring, and the stirring speed is 83 rpm;

Measure 315 kg of 40% glyoxal aqueous solution and pump it into the glyoxal high tank;

Measure 2760 kilograms of 30% NaOH solution and put it into the NaOH intermediate tank;

Use compressed air to press 1335 kg of carbon disulfide from the storage tank into the carbon disulfide intermediate tank (must ensure that the height of the water in the intermediate tank is not less than 15mm), press into the high carbon disulfide tank from the intermediate tank twice, and press about 700 kg for the first time , The remaining second time is pressed into the carbon disulfide high slot (must ensure that the height of the water in the high slot is not less than 15mm);

2. Synthesis of bis-piperazine: Under the condition of stirring in the first reaction kettle, pass the freezing liquid into the jacket of the first reaction kettle, wait until the temperature in the kettle is cooled to -4°C, and start to add 40% glyoxal aqueous solution dropwise to control The dripping rate keeps the reaction temperature at 3°C. After the dropwise addition of the glyoxal aqueous solution is completed, compressed air is used to press the materials from the first reactor to the second reactor. After the transfer of the materials is completed, steam is introduced into the jacket of the kettle, and the temperature is raised to 48°C within 20 minutes, and the reaction is carried out for 32 minutes. Open the steam valve, raise the temperature of the kettle to 56°C within 25 minutes, and continue the reaction for 32 minutes. Sampling was performed for liquid chromatography analysis. After the purity of the diopiperazine was qualified, the temperature of the kettle was reduced to 33°C, and a certain amount of water was added to the second reactor to adjust the concentration of the diopiperazine to about 25% by mass.

3. Add carbon disulfide dropwise to start the primary reaction of synthesis with TDDP as the main target product: press the bis-piperazine solution from the second reactor into the third reactor, and add 150 g of the catalyst tetramethylguanidine with a concentration of 30% 2590 kg of NaOH solution, fully stirred for 15 minutes, and at the same time pass the freezing liquid into the jacket of the third reactor. After the temperature in the reactor is cooled to 3℃, add carbon disulfide from the upper tank of carbon disulfide to the third reactor to control the reaction temperature in the reactor. It is 22°C; during this period, the remaining carbon disulfide is pressed from the middle tank into the high tank with compressed air according to the change of the level of the carbon disulfide high tank.

4. Secondary reaction: After the addition of carbon disulfide is completed, use compressed air to press the materials from the third synthesis kettle to the fourth synthesis kettle, and steam into the kettle jacket. The temperature is raised to 45°C in 25 minutes, and the reaction is continued at this temperature 42 minute.

5. Add water to the reaction solution, sample and analyze, including appearance, solid content, density, pH value, and pack and store after passing the test.

Example 2: Synthesis process of composite piperazine heavy metal chelating agent TDDP

1. Preparation of raw materials: After measuring 536 kg of ethylenediamine and sucking it into the first synthesis kettle with vacuum, add 170 g of tetrahydroquinoline, turn on the stirring, and the stirring speed is 83 rpm;

Measure 320 kilograms of 40% glyoxal aqueous solution and pump it into the glyoxal high tank;

Measure 2850 kilograms of 30% NaOH solution and put it into the intermediate tank;

Use compressed air to press 1355 kilograms of carbon disulfide from the storage tank into the carbon disulfide intermediate tank (must ensure that the height of the water in the intermediate tank is not less than 15mm), press into the high carbon disulfide tank from the intermediate tank twice, press about 700 kg for the first time , The remaining second time is pressed into the carbon disulfide high slot (must ensure that the height of the water in the high slot is not less than 15mm);

2. Synthesis of bis-piperazine: Under the stirring condition in the first reaction kettle, pass the freezing liquid into the jacket of the first reaction kettle. After the temperature in the kettle is cooled to -2°C, start to add 40% glyoxal aqueous solution dropwise to control The dripping rate keeps the reaction temperature at 7°C. After the dropwise addition of the glyoxal aqueous solution is completed, compressed air is used to press the materials from the first reaction kettle to the second reaction kettle, steam is introduced into the jacket of the kettle, the temperature is raised to 50°C within 25 minutes, and the reaction is carried out for 40 minutes. Open the steam valve, raise the temperature of the kettle to 58°C within 30 minutes, continue the reaction for 35 minutes, take a sample for liquid chromatography analysis, after the purity of the di-piperazine is qualified, reduce the kettle temperature to 32°C, and enter the second reaction kettle Add a certain amount of water to adjust the concentration of dioxopiperazine.

3. Add carbon disulfide dropwise, and start a reaction with TDDP as the main target product. Press the di-piperazine solution from the second reactor into the third reactor, and add 300 grams of the catalyst tetramethylguanidine and 30% NaOH. The solution is 2670 kg, fully stirred for 15 minutes, and at the same time, the freezing liquid is introduced into the jacket of the third reactor. After the temperature in the reactor is lowered to 4℃, carbon disulfide is added dropwise from the high tank of carbon disulfide to the third reactor, and the reaction temperature in the reactor is controlled to 25℃; During this period, the remaining carbon disulfide is pressed from the middle tank into the high tank with compressed air according to the change of the level of the carbon disulfide high tank.

4. After the secondary reaction carbon disulfide is added dropwise, use compressed air to press the materials from the third synthesis kettle to the fourth synthesis kettle, and steam into the kettle jacket. The temperature is raised to 45°C in 30 minutes, and the reaction is continued at this temperature for 45 minutes .

5. Add water to the reaction solution, take a sample and analyze it, and pack it into storage after passing the test.

Example 3: Synthesis process of composite piperazine heavy metal chelating agent TDDP

1. Preparation of raw materials: After measuring 538 kilograms of ethylenediamine and sucking it into the first synthesis kettle with vacuum, add 180 grams of tetrahydroquinoline, turn on the stirring, and the stirring speed is 83 rpm;

Measure 322 kilograms of 40% glyoxal aqueous solution and pump it into the glyoxal high tank;

Measure 2980 kilograms of 30% NaOH solution and put it into the intermediate tank;

Use compressed air to press 1365 kg of carbon disulfide from the storage tank into the carbon disulfide intermediate tank (must ensure that the height of the water in the intermediate tank is not less than 15mm), press into the high carbon disulfide tank from the intermediate tank twice, and press about 750 kg for the first time , The remaining second time is pressed into the carbon disulfide high slot (must ensure that the height of the water in the high slot is not less than 15mm);

2. Synthesis of bis-piperazine: Under the condition of stirring in the first reaction kettle, pass the freezing liquid into the jacket of the first reaction kettle, and after the temperature in the kettle is cooled to 0℃, start to add 40% glyoxal aqueous solution dropwise to control the drop. Accelerate to maintain the reaction temperature at 5°C. After the dropwise addition of the glyoxal aqueous solution is completed, compressed air is used to press the materials from the first reaction kettle to the second reaction kettle, steam is introduced into the jacket of the kettle, the temperature is raised to 50°C within 30 minutes, and the reaction is carried out for 45 minutes. Open the steam valve, raise the temperature of the kettle to 62°C within 30 minutes, continue the reaction for 45 minutes, take samples for liquid chromatography analysis, after the purity of the di-piperazine is qualified, reduce the kettle temperature to 30°C, and enter the second reaction kettle Add a certain amount of water to adjust the concentration of dioxopiperazine.

3. Add carbon disulfide dropwise to start the primary reaction of TDDP as the main target product synthesis: press the bis-piperazine solution from the second reactor into the third reactor, add 380 grams of tetramethylguanidine catalyst and 30% concentration 2785 kg of NaOH solution, fully stirred for 20 minutes, and at the same time pass the freezing liquid into the jacket of the third reactor. After the temperature in the reactor is cooled to 2℃, add carbon disulfide from the high tank of carbon disulfide to the third reactor to control the reaction temperature in the reactor. The temperature is 23°C; during this period, the remaining carbon disulfide is pressed from the middle tank into the high tank with compressed air according to the change of the level of the carbon disulfide high tank.

4. Secondary reaction: After the addition of carbon disulfide is completed, press the materials from the third synthesis kettle to the fourth synthesis kettle with compressed air, and steam the kettle jacket. The temperature is raised to 55°C in 35 minutes, and the reaction is continued at this temperature for 50 minutes. minute.

5. Add water to the reaction solution, take a sample and analyze it, and pack it into storage after passing the test.

Example 4: Synthesis process of composite piperazine heavy metal chelating agent TDDP

1. Preparation of raw materials: After measuring 540 kg of ethylenediamine and sucking it into the first synthesis kettle with vacuum, add 220 g of tetrahydroquinoline, turn on the stirring, and the stirring speed is 83 rpm;

Measure 322 kilograms of 40% glyoxal aqueous solution and pump it into the glyoxal high tank;

Measure 3000 kilograms of NaOH solution with a concentration of 30% and put it into the intermediate tank;

Use compressed air to press 1372 kg of carbon disulfide from the storage tank into the carbon disulfide intermediate tank (must ensure that the height of the water in the intermediate tank is not less than 15mm), press into the high carbon disulfide tank from the intermediate tank twice, and press about 750 kg for the first time , The remaining second time is pressed into the carbon disulfide high slot (must ensure that the height of the water in the high slot is not less than 15mm);

2. Synthesis of bis-piperazine: Under the condition of stirring in the first reaction kettle, pass the freezing liquid into the jacket of the first reaction kettle, and after the temperature in the kettle is cooled to 0℃, start to add 40% glyoxal aqueous solution dropwise to control the drop. Accelerate to maintain the reaction temperature at 9°C. After the dropwise addition of the glyoxal aqueous solution was completed, compressed air was used to press the materials from the first reaction kettle to the second reaction kettle, steam was introduced into the jacket of the kettle, the temperature was raised to 50°C within 35 minutes, and the reaction was carried out for 45 minutes. Open the steam valve, raise the temperature of the kettle to 65°C within 35 minutes, continue the reaction for 45 minutes, take samples for liquid chromatography analysis, and after the purity of the di-piperazine is qualified, reduce the kettle temperature to 30°C, and enter the second reaction kettle Add a certain amount of water to adjust the concentration of dioxopiperazine.

3. Add carbon disulfide dropwise to start the primary reaction of synthesis with TDDP as the main target product: press the bis-piperazine solution from the second reactor into the third reactor, add 450 g of tetramethylguanidine catalyst and 30% concentration 2880 kg of NaOH solution, fully stirred for 25 minutes, and at the same time pass the freezing liquid into the jacket of the third reactor. After the temperature in the reactor is cooled to 4℃, add carbon disulfide from the upper tank of carbon disulfide to the third reactor to control the reaction temperature in the reactor. The temperature is 28°C; during this period, the remaining carbon disulfide is pressed from the middle tank into the high tank with compressed air according to the change of the level of the carbon disulfide high tank.

4. Secondary reaction: After the addition of carbon disulfide is completed, use compressed air to press the materials from the third synthesis kettle to the fourth synthesis kettle, and steam into the kettle jacket. The temperature is raised to 50°C in 40 minutes, and the reaction is continued at this temperature. minute.

5. Add water to the reaction solution, take a sample and analyze it, and pack it into storage after passing the test.

Example 5: Synthesis process of composite piperazine heavy metal chelating agent TDDP

1. Preparation of raw materials: After measuring 540 kg of ethylenediamine and sucking it into the first synthesis kettle with vacuum, add 220 g of tetrahydroquinoline, turn on the stirring, and the stirring speed is 83 rpm;

Measure 322 kilograms of 40% glyoxal aqueous solution and pump it into the glyoxal high tank;

Measure 3050 kilograms of 30% NaOH solution and put it into the intermediate tank;

Use compressed air to press 1375 kg of carbon disulfide from the storage tank into the carbon disulfide intermediate tank (must ensure that the height of the water in the intermediate tank is not less than 15mm), press into the high carbon disulfide tank from the intermediate tank twice, press about 750 kg for the first time , The remaining second time is pressed into the carbon disulfide high slot (must ensure that the height of the water in the high slot is not less than 15mm);

2. Synthesis of bis-piperazine: Under the condition of stirring in the first reaction kettle, pass the freezing liquid into the jacket of the first reaction kettle, and after the temperature in the kettle is cooled to 0℃, start to add 40% glyoxal aqueous solution dropwise to control the drop. Accelerate to maintain the reaction temperature at 6°C. After the dropwise addition of the glyoxal aqueous solution is completed, compressed air is used to press the materials from the first reaction kettle to the second reaction kettle, steam is introduced into the jacket of the kettle, the temperature is raised to 50°C within 40 minutes, and the reaction is carried out for 45 minutes. Open the steam valve, raise the temperature of the kettle to 62°C within 40 minutes, continue the reaction for 45 minutes, take a sample for liquid chromatography analysis, after the purity of the di-piperazine is qualified, reduce the kettle temperature to 30°C, and enter the second reaction kettle Add a certain amount of water to adjust the concentration of dioxopiperazine.

3. Add carbon disulfide dropwise to start a reaction of synthesis of TDDP as the main target product: press the bis-piperazine solution from the second reactor into the third reactor, add 500 g of the catalyst tetramethylguanidine and 30% concentration 3030 kg of NaOH solution, fully stirred for 25 minutes, and at the same time pass the freezing liquid into the jacket of the third reactor. After the temperature in the reactor is cooled to 5℃, add carbon disulfide from the high tank of carbon disulfide to the third reactor to control the reaction temperature in the reactor. It is 27°C; during this period, the remaining carbon disulfide is pressed from the middle tank into the high tank with compressed air according to the change of the level of the carbon disulfide high tank.

4. Secondary reaction: After the addition of carbon disulfide is completed, use compressed air to press the materials from the third synthesis kettle to the fourth synthesis kettle, and steam into the kettle jacket. The temperature will increase to 55°C in 35 minutes, and the reaction will continue at this temperature for 60 minutes. minute.

5. Add water to the reaction solution, take a sample and analyze it, and pack it into storage after passing the test.

In Examples 1 to 5, the quality index analysis results of the prepared products are summarized as shown in Table 1.

Table 1 Summary of product quality index analysis results prepared

The solid content in Table 1 refers to the weight ratio of the solid obtained after drying the final product solution to the solution.

In the synthesis process provided by the present invention, the jacket of the first reactor and the third reactor only passes the refrigerated liquid, and the jacket of the second reactor and the fourth reactor is only heated by steam. In this way, the cooling and heating process is Crossing in different reactors. During the production process, the temperature in the same reactor does not fluctuate much to avoid excessive energy consumption caused by cross-over of cold and heat. The invention realizes stage control of temperature by transferring materials to different reaction kettles, which not only ensures the stability of reaction temperature control, but also avoids time-consuming problems caused by rising and falling temperatures, improves reaction efficiency and reduces energy consumption.

Example 6, Removal of single component heavy metal ion application test

Prepare water samples containing Cu ²⁺ , Zn ²⁺ , Cd ²⁺ , Pb ²⁺ , Ni ^{2+ to} simulate heavy metals, add 100 mg/L of the heavy metal trap prepared in Example 5, and stir for 5 min at 100 r/min After standing for filtration, the supernatant was taken to determine the concentration of heavy metal ions. The treatment effect is shown in Table 2.

Table 2 The removal effect of the product of the present invention on free heavy metal ions

Ion category	Cu 2+	Zn 2+	Cd 2+	Pb 2+	Ni 2+
Initial concentration (mg/L)	80.09	81.33	81.86	80.54	81.29
Concentration after treatment (mg/L)	0.12	0.65	0.04	0.11	0.37
Removal rate (%)	99.85	99.20	99.95	99.86	99.54
Emission standard (mg/L)	0.5	1.5	0.05	0.2	0.5
process result	Up to standard	Up to standard	Up to standard	Up to standard	Up to standard

It can be seen that the product of the present invention ^{has a good removal effect on free Cu 2+} , Zn ²⁺ , Cd ²⁺ , Pb ²⁺ , Ni ²⁺ and other heavy metal ions, and the residual ion concentration is lower than the national first-level comprehensive sewage discharge standard .

Example 7, Removal of coexisting multi-component heavy metal ions in the solution

Using electroplating wastewater from a company in Weifang, Shandong, the measured Cu ²⁺ concentration was 102.54 mg/L, Zn ²⁺ concentration was 17.41 mg/L, Mn ²⁺ concentration was 0.15 mg/L, and Pb ²⁺ concentration was 2.11 mg/L. , Ni ²⁺ concentration is 23.66mg/L. Add 200mg/L of the heavy metal trapping agent of Example 5, the stirring rate is 100r/min, the reaction is stirred for 5 minutes, and then stand and filter, and the supernatant is taken to determine the concentration of the above five metal ions. The results are shown in Table 3 below. Meet the national emission standards.

Table 3 Experiment of removing coexisting multi-component heavy metal ions in solution

Ion category	Cu 2+	Zn 2+	Mn 2+	Pb 2+	Ni 2+
Initial concentration (mg/L)	102.54	17.41	0.15	2.11	23.66
Concentration after treatment (mg/L)	0.24	not detected	not detected	0.05	0.25
Removal rate (%)	99.77	-	-	97.63	98.94
Emission standard (mg/L)	0.5	1.5	0.05	0.2	0.5
process result	Up to standard	Up to standard	Up to standard	Up to standard	Up to standard

Example 8 Removal of heavy metal ions in waste incineration fly ash application experiment

Among them, the fly ash is the fly ash during the normal operation of a garbage incineration power plant in Shandong; the chelating agent uses the sample prepared in Example 5.

In the mixer, the sample prepared in Example 5: fly ash: water was mixed and stirred in a ratio of 1:55:15, and after 2 hours of reaction, the fly ash mass was cured for three days. After three days, the cured fly ash solidified block was taken out and leached according to "HJ/T 300-2007 Solid Waste Leaching Toxicity Leaching Method Acetic Acid Buffer Solution Method", cf. "GB16889-2008 Heavy Metal Concentration of Domestic Waste Landfill Pollution Control Standard" For the limit values of the content of six heavy metals such as copper, nickel, and cadmium, the concentration of heavy metals in the leaching solution of the fly ash solidified block is detected. The application effect is shown in Table 4.

Table 4 Analysis results of heavy metal content and leaching concentration in fly ash

The test results listed in Table 4 show that the use of the fly ash heavy metal chelating agent of the present invention to solidify and stabilize the fly ash, the solidified block heavy metals are copper, cadmium, etc. as examples, and the leaching concentration meets the GB16889-2008 limit. The national hazardous waste identification standards and the entry standards for domestic waste landfills have been implemented.

The above descriptions are only preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. A synthetic process for the composite piperazine heavy metal chelating agent TDDP, which is characterized in that it includes the following reactions:

   Using ethylenediamine and glyoxal as raw materials, a condensation reaction occurs in the presence of a catalyst to produce dioxopiperazine; using organic base tetramethylguanidine as a catalyst, dioxopiperazine reacts with carbon disulfide and sodium hydroxide to produce TDDP; simultaneously The reaction of ethylenediamine with carbon disulfide and sodium hydroxide generates EDTC.
2. The synthesis process of a composite piperazine heavy metal chelating agent TDDP according to claim 1, wherein the synthesis process comprises the following steps:

   Step 1. Material preparation: After measuring the ethylenediamine, suck it into the first reaction kettle with a vacuum, add the catalyst, and turn on the stirring;

   Prepare glyoxal into a glyoxal aqueous solution, and pump it into the glyoxal high tank;

   Prepare NaOH solution and pump it into the NaOH intermediate tank;

   Use compressed air to press carbon disulfide from the storage tank into the carbon disulfide intermediate tank, and press it into the carbon disulfide high tank twice;

   Step 2. Synthesis of diopiperazine: Under the state of stirring and starting, pass the cooling liquid into the jacket of the first reactor, and wait until the temperature in the first reactor drops to -5～0℃, and then start to feed the first reactor. Add glyoxal aqueous solution dropwise to control the dropping rate to maintain the reaction temperature at 2～10℃;

   After the dropwise addition of the glyoxal aqueous solution is completed, use compressed air to press the materials from the first reactor to the second reactor, and steam the jacket of the second reactor, heat up to 47～52℃, and react for 30～50 minutes; , Open the steam valve, raise the temperature of the kettle to 55～67℃, continue the reaction for 30～50 minutes; reduce the temperature of the kettle below 35℃, add a certain amount of water to the second reactor to adjust the concentration of dioxopiperazine ；

   Step 3. Synthesis of TDDP as the main target product: Use compressed air to press the product obtained in step 2 from the second reactor into the third reactor, add the catalyst tetramethylguanidine and NaOH solution, and stir fully; to the third reactor Cooling liquid is passed into the jacket, and after the temperature in the kettle is reduced to 0～5℃, carbon disulfide is added dropwise to the third reactor from the upper tank of carbon disulfide, and the reaction temperature in the reactor is controlled to be 20～32℃;

   Step 4. Secondary reaction: Step 3 After the addition of carbon disulfide is completed, use compressed air to press the product obtained in Step 3 from the third reactor into the fourth reactor, and steam into the jacket of the fourth reactor to make the inside of the reactor The temperature is increased to 45-60°C in 20-50 minutes, and the reaction is continued at this temperature for 40-70 minutes;

   Step 5. After the reaction is over, add water to the reaction liquid of the fourth reactor, take samples and analyze, and after the test is qualified, pack and store.
3. The synthesis process of a composite piperazine heavy metal chelating agent TDDP according to claim 2, wherein the catalyst in step one is tetrahydroquinoline.
4. The synthesis process of a composite piperazine heavy metal chelating agent TDDP according to claim 2, wherein the molar ratio of glyoxal to ethylenediamine in step one is 1: (4.01-4.09).
5. The synthesis process of a composite piperazine heavy metal chelating agent TDDP according to claim 2, wherein the molar ratio of said glyoxal to carbon disulfide is 1: (8.06-8.12).
6. The synthesis process of a composite piperazine heavy metal chelating agent TDDP according to claim 2, wherein the molar ratio of the glyoxal to NaOH is 1: (8.8-10.4).
7. The synthesis process of a composite piperazine heavy metal chelating agent TDDP according to claim 3, wherein the amount of the catalyst tetrahydroquinoline is 0.02-0.2% of the weight of glyoxal.
8. The synthesis process of a composite piperazine heavy metal chelating agent TDDP according to claim 2, wherein the amount of the catalyst tetramethyl biguanide is 0.05-0.5% by weight of glyoxal.